Memory controller, memory system and operating method of memory device

ABSTRACT

A memory controller includes a block ratio calculator configured to calculate a ratio of free blocks among memory blocks for storing data; a policy selector configured to select, based on the calculated ratio of free blocks, any one garbage collection policy of a first garbage collection policy of specifying priorities to be used to select a victim block depending on attributes of the data, and a second garbage collection policy of specifying the priorities to be used to select the victim block regardless of the attributes of the data; and a garbage collection performing component configured to perform a garbage collection operation on at least one memory block of the memory blocks according to the garbage collection policy selected by the policy selector.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.16/367,492 filed on Mar. 28, 2019, which claims benefits of Koreanpatent application number 10-2018-0106192, filed on Sep. 5, 2018. Thedisclosure of each of the foregoing application is incorporated hereinby reference in its entirety.

BACKGROUND 1. Field of Invention

Various embodiments of the present disclosure generally relate to amemory controller and a memory system including the same, and moreparticularly, to a memory controller and a memory system including thesame capable of efficiently performing a garbage collection operation.

2. Description of Related Art

Memory systems may include a memory controller and a memory device.

The memory device may store data or output the stored data, undercontrol of the memory controller. For example, the memory device can beformed of volatile memory devices in which data stored therein is lostwhen power is turned off, or nonvolatile memory devices which can retaindata stored therein even when power supply is interrupted.

SUMMARY

Various embodiments of the present disclosure are directed to a memorycontroller and a memory system including the same capable of efficientlyperforming a garbage collection operation.

An embodiment of the present disclosure may provide for a memorycontroller including a block ratio calculator configured to calculate aratio of free blocks among a plurality of memory blocks for storingdata; a policy selector configured to select, based on the calculatedratio of free blocks, any one garbage collection policy of a firstgarbage collection policy of specifying priorities to be used to selecta victim block depending on attributes of the data, and a second garbagecollection policy of specifying the priorities to be used to select thevictim block regardless of the attributes of the data; and a garbagecollection performing component configured to perform a garbagecollection operation on at least one memory block of the plurality ofmemory blocks according to the garbage collection policy selected by thepolicy selector.

An embodiment of the present disclosure may provide for a memory systemincluding a memory device including a plurality of memory blocks; and amemory controller configured to receive, from a host, program data and aprogram request including attribute information of the program data,configure page data by adding the attribute information of the programdata to the program data, and control the memory device to program thepage data to any one memory block of the plurality of memory blocks.

An embodiment of the present disclosure may provide for an operatingmethod of a memory device including selecting, as a victim block, afirst memory block storing a greatest number of pieces of cold data whena number of free blocks is equal to or greater than a first threshold,and a second memory block having a smallest number of valid pages whenthe number of free blocks is less than the first threshold; performing agarbage collection operation on the selected victim block; andincreasing the first threshold when a selection ratio of the firstmemory block to the second memory block is greater than a secondthreshold and decreasing the first threshold when the selection ratio isless than the second threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a memory system in accordance with anembodiment of the present disclosure.

FIG. 2 is a diagram illustrating the memory controller shown in FIG. 1 .

FIG. 3 is a diagram illustrating an operation of programming page datato a memory block in accordance with an embodiment of the presentdisclosure.

FIG. 4 is a diagram for describing a garbage collection policy inaccordance with an embodiment of the present disclosure.

FIG. 5 is a diagram for describing a process of selecting a garbagecollection policy and a victim block in accordance with an embodiment ofthe present disclosure.

FIGS. 6 to 8 are diagrams for describing a process of performing agarbage collection operation according to a first garbage collectionpolicy in accordance with an embodiment of the present disclosure.

FIG. 9 is a flowchart for describing a method of operating the memorycontroller in accordance with an embodiment of the present disclosure.

FIG. 10 is a flowchart for describing a method of operating the memorycontroller in accordance with an embodiment of the present disclosure.

FIG. 11 is a diagram for describing a memory device in accordance withan embodiment of the present disclosure.

FIG. 12 is a diagram illustrating a memory block in accordance with anembodiment of the present disclosure.

FIG. 13 is a diagram illustrating a memory block having athree-dimensional structure in accordance with an embodiment of thepresent disclosure.

FIG. 14 is a diagram illustrating a memory block having athree-dimensional structure in accordance with an embodiment of thepresent disclosure.

FIGS. 15 to 18 are diagrams illustrating various examples of a memorysystem including the memory controller shown in FIGS. 1 and 2 .

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the example embodiments to those skilled in the art.

In the drawing figures, dimensions may be exaggerated for clarity ofillustration. It will be understood that when an element is referred toas being “between” two elements, it can be the only element between thetwo elements, or one or more intervening elements may also be present.

Hereinafter, embodiments will be described with reference to theaccompanying drawings. Embodiments are described herein with referenceto cross-sectional illustrations that are schematic illustrations ofembodiments (and intermediate structures). As such, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, embodimentsshould not be construed as limited to the particular shapes of regionsillustrated herein but may include deviations in shapes that result, forexample, from manufacturing. In the drawings, lengths and sizes oflayers and regions may be exaggerated for clarity. Like referencenumerals in the drawings denote like elements.

Terms such as “first” and “second” may be used to describe variouscomponents, but they should not limit the various components. Thoseterms are only used for the purpose of differentiating a component fromother components. For example, a first component may be referred to as asecond component, and a second component may be referred to as a firstcomponent and so forth without departing from the spirit and scope ofthe present disclosure. Furthermore, “and/or” may include any one of ora combination of the components mentioned.

Furthermore, a singular form may include a plural from as long as it isnot specifically mentioned in a sentence. Furthermore,“include/comprise” or “including/comprising” used in the specificationrepresents that one or more components, steps, operations, and elementsexist or are added.

Furthermore, unless defined otherwise, all the terms used in thisspecification including technical and scientific terms have the samemeanings as would be generally understood by those skilled in therelated art. The terms defined in generally used dictionaries should beconstrued as having the same meanings as would be construed in thecontext of the related art, and unless clearly defined otherwise in thisspecification, should not be construed as having idealistic or overlyformal meanings.

It is also noted that in this specification, “connected/coupled” refersto one component not only directly coupling another component but alsoindirectly coupling another component through an intermediate component.On the other hand, “directly connected/directly coupled” refers to onecomponent directly coupling another component without an intermediatecomponent.

FIG. 1 is a diagram illustrating a memory system 2000 in accordance withan embodiment of the present disclosure.

Referring to FIG. 1 , the memory system 2000 may include a memory device2200 configured to store data, and a memory controller 2100 configuredto control the memory device 2200 according to requests of a host 1000.

The host 1000 may communicate with the memory system 2000 using at leastone of various interface protocols such as a non-volatile memory express(NVMe) protocol, a peripheral component interconnection-express (PCI-eor PCIe) protocol, an advanced technology attachment (ATA) protocol, aserial ATA (SATA) protocol, a parallel ATA (PATA) protocol, a universalserial bus (USB) protocol, a multimedia card (MMC) protocol, an enhancedsmall disk interface (ESDI) protocol, an integrated drive electronics(IDE) protocol, a mobile industry processor interface (MIPI) protocol, auniversal flash storage (UFS) protocol, a small computer small interface(SCSI) protocol, and a serial attached SCSI (SAS) protocol. However,embodiments of the present disclosure are not limited to this.

The memory controller 2100 may control the overall operation of thememory system 2000 and data exchange between the host 1000 and thememory device 2200. For instance, during a program operation, the memorycontroller 2100 may transmit a command, an address, data, etc. to thememory device 2200. During a read operation, the memory controller 2100may transmit a command, an address, etc. to the memory device 2200. Thememory controller 2100 may perform a garbage collection operation on aplurality of memory blocks included in the memory device 2200.

The memory device 2200 may be formed of a volatile memory device 2200 inwhich data stored therein is lost when power is turned off, or anonvolatile memory device which can retain data stored therein even whenpower supply is interrupted. The memory device 2200 may perform aprogram operation, a read operation, an erase operation, a garbagecollection operation, etc. under control of the memory controller 2100.The memory device 2200 may include a plurality of memory blocksconfigured to store data. Each memory block may include a plurality ofpages configured to store data. Each page may include a normal area inwhich user data may be stored, and a spare area in which meta data forthe user data may be stored. The user data may be system data, mediadata, or text data which is generated by an operating system or variousapplications, but embodiments of the present disclosure are not limitedthereto.

FIG. 2 is a diagram illustrating the memory controller 2100 shown inFIG. 1 .

The memory controller 2100 in accordance with an embodiment of thepresent disclosure may receive program data and a program request fromthe host 1000. The program data may refer to data to be programmed tothe memory device 2200. The program request may include attributeinformation of the program data. The attribute information of theprogram data may be information indicating whether the program data ishot data or cold data. It may be determined whether the program data ishot data or cold data depending on the type or size of the data. Forexample, data having a relatively large size may be classified as colddata, and data having a relatively small size may be classified as hotdata. For instance, media data may be classified as cold data, andsystem data may be classified as hot data.

Generally, to program program data received from the host 1000 to thememory device 2200, a conventional memory controller is required todesignate a plurality of memory blocks as open blocks and respectivelystore hot data and cold data in different open blocks.

However, when programming program data to the memory device 2200, thememory controller 2100 in accordance with an embodiment of the presentdisclosure may further program information about whether the programdata is hot data or cold data. Therefore, the memory controller 2100 inaccordance with an embodiment of the present disclosure may designateonly one memory block as an open block so as to program the program datareceived from the host 1000 to the memory device 2200.

Referring to FIG. 2 , the memory controller 2100 in accordance with anembodiment of the present disclosure may include a host interface 2110,a central processing unit 2120, a memory interface 2130, a buffer memory2140, an error correction circuit 2150, and an internal memory 2160. Thehost interface 2110, the memory interface 2130, the buffer memory 2140,the error correction circuit 2150, and the internal memory 2160 may becontrolled by the central processing unit 2120.

The host interface 2110 may perform data exchange with the host 1000using various interface protocols. For example, the host interface 2110may communicate with the host 1000 using at least one of variousinterface protocols such as a non-volatile memory express (NVMe)protocol, a peripheral component interconnection-express (PCI-E)protocol, an advanced technology attachment (ATA) protocol, a serial ATA(SATA) protocol, a parallel ATA (PATA) protocol, a universal serial bus(USB) protocol, a multimedia card (MMC) protocol, an enhanced small diskinterface (ESDI) protocol, an integrated drive electronics (IDE)protocol, a mobile industry processor interface (MIPI) protocol, auniversal flash storage (UFS) protocol, a small computer small interface(SCSI) protocol, and a serial attached SCSI (SAS) protocol. However,embodiments of the present disclosure are not limited to this.

The host interface 2110 may transmit program data received from the host1000 to the buffer memory 2140, and transmit a program request receivedfrom the host 1000 to the central processing unit 2120.

The central processing unit 2120 may perform various operations orgenerate a command and an address so as to control the memory device2200. For example, the central processing unit 2120 may generate variouscommands needed for a program operation, a read operation, an eraseoperation, a garbage collection operation.

The central processing unit 2120 may translate a logical addressinputted from the host 1000 to a physical address so as to control theoperation of the memory device 2200. The central processing unit 2120may use an address mapping table stored in the internal memory 2160 totranslate a logical address to a physical address or translate aphysical address to a logical address. The central processing unit 2120may update the address mapping table when new data is programmed to thememory device 2200 or data that has been stored in the memory device2200 is erased.

The central processing unit 2120 may include a program operationcontroller 2122, and a garbage collection operation controller 2124.

The program operation controller 2122 may control a program operationfor programming program data received from the host 1000 to the memorydevice 2200. The program operation controller 2122 may include a pagedata configurator 2122 a and a command generator 2122 b.

The page data configurator 2122 a may receive a program request andconfigure page data in response to the program request. The page datamay refer to data that is to be stored or has been stored in any one ofa plurality of pages included in a memory block.

The page data configurator 2122 a may configure the page data byextracting data attribute information included in the program requestand adding the extracted data attribute information to the program datastored in the buffer memory 2140. In other words, the page data mayinclude program data and attribute information corresponding to theprogram data. When the page data is configured, the page dataconfigurator 2122 a may notify the command generator 2122 b that thepage data has been configured.

The command generator 2122 b may generate a program command to instructthe page data to be programmed and an address, and transmit the programcommand and the address to the memory device 2200. The command generator2122 b may control the buffer memory 2140 so that the page data that hasbeen temporarily stored in the buffer memory 2140 may be transmitted tothe memory device 2200. When notified from the page data configurator2122 a that the page data has been configured, the command generator2122 b may generate the program command and the address.

The garbage collection operation controller 2124 may control a garbagecollection operation on a plurality of memory blocks included in thememory device 2200. The garbage collection operation controller 2124 mayinclude a block ratio calculator 2124 a, a policy selector 2124 b, agarbage collection performing component 2124 c, a policy storage 2124 d,and a threshold value manager 2124 e.

The block ratio calculator 2124 a may calculate the ratio of free blocksamong the memory blocks included in the memory device 2200. In otherwords, the block ratio calculator 2124 a may calculate the ratio of thenumber of free blocks to which no data is written among the total numberof memory blocks. Here, the total number of memory blocks may includethe number of OP bocks allocated for over-provisioning (OP). An OP blockmay be an area allocated for performance management of the memorysystem.

In an embodiment, the ratio of free blocks may be calculated withreference to the address mapping table stored in the internal memory2160. For example, the address mapping table may have information aboutthe physical addresses of all of the memory blocks and information aboutthe physical addresses of memory blocks storing data. Therefore, theblock ratio calculator 2124 a may calculate the total number of memoryblocks with reference to the information about the physical addresses ofall of the memory blocks, and may calculate the number of free blockswith reference to the information about the physical addresses of memoryblocks storing data. The block ratio calculator 2124 a may calculate theratio of free blocks, based on the calculated total number of memoryblocks and the calculated number of free blocks.

The policy selector 2124 b may select a garbage collection policy for agarbage collection operation to be currently performed among a pluralityof garbage collection policies. For example, the policy selector 2124 bmay select a garbage collection policy for a garbage collectionoperation to be currently performed, based on the ratio of free blockscalculated by the block ratio calculator 2124 a.

The garbage collection policy may include any one of a first garbagecollection policy for specifying priorities to be used to select avictim block, depending on the attributes of data, and a second garbagecollection policy for specifying priorities to be used to select avictim block regardless of the attributes of data. However, embodimentsof the present disclosure are not limited to this.

For example, the first garbage collection policy may specify that amemory block storing a greater number of pieces of cold data has ahigher priority when a victim block is selected. Furthermore, the firstgarbage collection policy may further specify priorities to be used toselect victim data in the selected victim block, depending on theattributes of corresponding data. For example, the first garbagecollection policy may specify that the priority of cold data is higherthan that of hot data when victim data is selected in the selectedvictim block.

For example, the second garbage collection policy may specify prioritiesto be used to select a victim block, depending on the number of validpages included in each memory block. For instance, the second garbagecollection policy may specify that a memory block having smaller numberof valid pages has a higher priority when a victim block is selected.

For example, the policy selector 2124 b may select the first garbagecollection policy when the ratio of free blocks is a first thresholdvalue or more, and may select the second garbage collection policy whenthe ratio of free blocks is less than the first threshold value. Forexample, on the assumption that the first threshold value is 0.15, whenthe ratio of free blocks is 0.2, the first garbage collection policy maybe selected, and, when the ratio of free blocks is 0.1, the secondgarbage collection policy may be selected. The first threshold value maybe adjusted depending on ratios of the first and second garbagecollection policy selected when the garbage collection operation isperformed. Detailed descriptions pertaining to this will be made indescriptions of related parts.

The garbage collection performing component 2124 c may perform a garbagecollection operation according to a selected garbage collection policy.

For example, in the case where the first garbage collection policy isselected, the garbage collection performing component 2124 c maypreferentially select, as a victim block, at least one memory block thatincludes the larger number of pieces of cold data among the memoryblocks. The garbage collection performing component 2124 c maypreferentially perform the garbage collection operation on page dataincluding cold data among page data stored in the selected victim block.In the case where the garbage collection operation on the page dataincluding the cold data among the page data stored in the victim blockhas been completed or the number of pieces of page data including colddata is not enough to fill the entirety of one memory block, the garbagecollection performing component 2124 c may perform a garbage collectionoperation on page data including hot data.

For instance, in the case where the second garbage collection policy isselected, the garbage collection performing component 2124 c maypreferentially perform a garbage collection operation on a memory blockhaving the least number of valid pages among the memory blocks

The policy storage 2124 d may store various garbage collection policiesfor garbage collection operations. For example, the policy storage 2124d may store the first garbage collection policy and the second garbagecollection policy.

The threshold value manager 2124 e may set or adjust the first thresholdvalue. For example, the threshold value manager 2124 e may adjust thefirst threshold value depending on selection ratios of the first garbagecollection policy and the second garbage collection policy. Forinstance, the threshold value manager 2124 e may receive, from thepolicy storage 2124 d, information about which garbage collectionpolicies were selected for previously-performed garbage collectionoperations, and manage the information as history information. Thethreshold value manager 2124 e may analyze the history information anddetermine the selection ratios of the garbage collection policiesselected during the previously-performed garbage collection operations.For example, the threshold value manager 2124 e may analyze the historyinformation and determine the number of times the first garbagecollection policy has been selected per one selection of the secondgarbage collection policy.

The threshold value manager 2124 e may increase the first thresholdvalue as the ratio at which the first garbage collection policy has beenselected is increased, per single selection of the second garbagecollection policy, and may reduce the first threshold value as the ratioat which the first garbage collection policy has been selected isreduced, per single selection of the second garbage collection policy.For example, the threshold value manager 2124 e may store a secondthreshold value as a reference value for adjusting the first thresholdvalue. In the case where the ratio at which the first garbage collectionpolicy has been selected exceeds the second threshold value, thethreshold value manager 2124 e may increase the first threshold value bya set value. In the case where the ratio at which the first garbagecollection policy has been selected is less than the second thresholdvalue, the threshold value manager 2124 e may reduce the first thresholdvalue by a set value. For instance, on the assumption that the firstthreshold value is 0.15 and the second threshold value is 0.1, if theratio at which the first garbage collection policy has been selected is0.11, the first threshold value is adjusted to 0.16, and if the ratio atwhich the first garbage collection policy has been selected is 0.09, thefirst threshold value is adjusted to 0.14. The reason for this isbecause of the fact that if the first garbage collection policy ofspecifying a cold data priority policy is excessively frequentlyselected, the garbage collection efficiency may be reduced in specificcircumstances.

The memory interface 2130 may communicate with the memory device 2200using various interface protocols.

The buffer memory 2140 may temporarily store data while the memorycontroller 2100 controls the memory device 2200. For example, datareceived from the host 1000 may be temporarily stored in the buffermemory 2140 until the program operation is completed. Furthermore, dataread from the memory device 2200 during a read operation may betemporarily stored in the buffer memory 2140.

The error correction circuit 2150 may perform an error correctionencoding during a program operation and an error correction decodingduring a read operation.

The internal memory 2160 may be used as a storage for storing variousinformation needed for the operation of the memory controller 2100. Theinternal memory 2160 may store a plurality of tables. For example, theinternal memory 2160 may store an address mapping table in which logicaladdresses and physical addresses are mapped.

FIG. 3 is a diagram illustrating an operation of programming page datato a memory block in accordance with an embodiment of the presentdisclosure.

Referring to FIG. 3 , the memory block may include a plurality of pages.Each page may include a normal area and a spare area.

As described above, page data may include user data and attributeinformation of the user data. A piece of page data may be programmed toone page.

In FIG. 3 , there is illustrated the case where attribute informationdesignated by ‘0’ indicates that user data is cold data, and attributeinformation designated by ‘1’ indicates that user data is hot data.

As described above, cold data and hot data may be stored in one openblock. Hence, costs required for the memory controller to manage theopen block may be reduced.

FIG. 4 is a diagram for describing the garbage collection policy inaccordance with an embodiment of the present disclosure.

Although FIG. 4 illustrates two policies including the first garbagecollection policy and the second garbage collection policy by way ofexample, various other garbage collection policies may be employed.

The first garbage collection policy may specify priorities to be used toselect a victim block and victim data, depending on attributes of data.For example, the first garbage collection policy may specify that amemory block storing a greater number of pieces of cold data has ahigher priority when a victim block is selected. Furthermore, the firstgarbage collection policy may specify that the priority of cold data ishigher than that of hot data when victim data is selected in theselected victim block.

The second garbage collection policy may specify priorities to be usedto select a victim block, depending on the number of valid pages. Forinstance, the second garbage collection policy may specify that a memoryblock having a smaller number of valid pages has a higher priority.

FIG. 5 is a diagram for describing a process of selecting a garbagecollection policy and a victim block in accordance with an embodiment ofthe present disclosure.

FIG. 5 illustrates the case where the memory device includes six memoryblocks. Furthermore, in FIG. 5 , there is illustrated the case whereuser data is written to three memory blocks Block 1, Block 2, and Block3, and no user data is written to three memory blocks Block 4, Block 5,and Block 6. In other words, three memory blocks Block 4, Block 5, andBlock 6 are free blocks. At least one of memory blocks Block 4, Block 5,and Block 6 may be an OP block. Furthermore, FIG. 5 illustrates onlynormal areas and areas in which attribute information is stored amongspare areas. In other words, FIG. 5 illustrates only page data amongdata stored in the memory blocks.

As described above, the memory controller may select a garbagecollection policy based on the ratio of free blocks to all memoryblocks.

For example, the memory controller may select the first garbagecollection policy when the ratio of free blocks is the first thresholdvalue or more, and may select the second garbage collection policy whenthe ratio of free blocks is less than the first threshold value. When itis assumed that the first threshold value is set to 0.5, the ratio offree blocks is 0.5 in the embodiment shown in FIG. 5 , so that the firstgarbage collection policy may be selected.

The memory controller may select a victim block according to theselected garbage collection policy. When the first garbage collectionpolicy has been selected, the memory controller may select, as a victimblock, at least one memory block storing a greater number of pieces ofcold data among the memory blocks Block 1 to Block 3.

In the embodiment described with reference to FIG. 5 , attributeinformation ‘0’ indicates that user data is cold data, and attributeinformation ‘1’ indicates that user data is hot data. Therefore, theembodiment shown in FIG. 5 indicates the case where two pieces of colddata are stored in each of memory block Block 1 and memory block Block2, and four pieces of cold data are stored in memory block Block 3.

When only one memory block is selected as a victim block, the memorycontroller may select, as the victim block, the memory block Block 3having the largest number of pieces of cold data.

FIGS. 6 to 8 are diagrams for describing a process of performing thegarbage collection operation according to the first garbage collectionpolicy in accordance with an embodiment of the present disclosure. FIGS.6 to 8 illustrate only normal areas and areas in which attributeinformation is stored among spare areas. In other words, FIGS. 6 to 8illustrate only page data among data stored in the memory blocks. In theembodiment described with reference to FIGS. 6 to 8 , attributeinformation ‘0’ indicates that user data is cold data, and attributeinformation ‘1’ indicates that user data is hot data. In FIG. 6 , thereis illustrated the case where three target blocks are selected toperform a garbage collection operation for page data programmed to threevictim blocks.

In FIG. 7 , there is illustrated the case where a garbage collectionoperation is preferentially performed on page data 702, 704, 706including cold data among page data programmed to victim blocksaccording to the first garbage collection policy. In the case where thefirst garbage collection policy is selected, the memory controller maypreferentially perform the garbage collection operation on page dataincluding cold data with reference to attribute information included ineach page data. In other words, the memory controller may preferentiallyperform the garbage collection operation on the page data 702, 704, and706 including attribute information ‘0’. Referring to FIG. 7 , it can beunderstood that the page data 702, 704, and 706 including attributeinformation ‘0’ has been moved to one of the target blocks bypreferentially performing the garbage collection operation on thecorresponding page data 702, 704, and 706.

In the case where the garbage collection operation on the page dataincluding the cold data has been completed or the number of pieces ofpage data including cold data is not enough to fill one memory block, agarbage collection operation may be performed on page data including hotdata. Referring to FIG. 8 , it can be understood that page dataincluding attribute information ‘1’ has been moved to the target blocksby performing the garbage collection operation on the corresponding pagedata.

FIG. 9 is a flowchart for describing a method of operating the memorycontroller in accordance with an embodiment of the present disclosure.

At step S901, the memory controller may receive program data and aprogram request from the host. The program request may include attributeinformation indicating attributes of the program data. The attributeinformation may be information about whether the program data is hotdata or cold data.

At step 903, the memory controller may configure page data. For example,the memory controller may configure the page data by extractingattribute information included in the program request received from thehost and adding the extracted attribute information to the program data.

At step 905, the memory controller may generate a program command and anaddress to program the page data to the memory device. The memorycontroller may transmit the program command, the address, and the pagedata to the memory device.

FIG. 10 is a flowchart for describing a method of operating the memorycontroller in accordance with an embodiment of the present disclosure.The embodiment to be described with reference to FIG. 10 may be appliedto steps to be performed after the steps described with reference toFIG. 9 , but various embodiments of the present disclosure are notlimited thereto. In some embodiment, at least one of the steps shown inFIG. 10 can be omitted, and the sequence of the steps can be changed.

At step 1001, the memory controller may calculate the ratio of freeblocks. For example, the memory controller may calculate the ratio ofthe number of free blocks in the number of total memory blocks includedin the memory device.

At step 1003, the memory controller may determine whether the ratio offree blocks is the first threshold value or more. If the ratio of freeblocks is the first threshold value or more (“Y” at step 1003), step1005 a proceeds so that the first garbage collection policy may beselected. If the ratio of free blocks is less than the first thresholdvalue (refer to ‘N’), step 1005 b proceeds so that the second garbagecollection policy may be selected. If the first garbage collectionpolicy or the second garbage collection policy is selected, step 1007may proceed.

At step 1007, the memory controller may perform a garbage collectionoperation based on the selected garbage collection policy. In anembodiment, if the first garbage collection policy is selected, thememory controller may select, as a victim block, at least one memoryblock storing a greater number of pieces of cold data. Furthermore, thememory controller may preferentially perform a garbage collectionoperation on page data including cold data among page data included inthe selected victim block. Thereafter, in the case where there is nomore page data including cold data among the page data included in thevictim block or the number of pieces of page data including cold data isnot enough to fill one memory block, the memory controller may perform agarbage collection operation on page data including hot data. In anembodiment, if the second garbage collection policy is selected, thememory controller may preferentially perform a garbage collectionoperation on a memory block having the least number of valid pages amongthe memory blocks.

At step 1009, the memory controller may calculate a garbage collectionpolicy selection ratio. For example, the memory controller may manageinformation about what garbage collection policies were selected forpreviously-performed garbage collection operations as historyinformation, and determine a ratio between the garbage collectionpolicies selected for the previously-performed garbage collectionoperations by analyzing the history information. For example, the memorycontroller may analyze the history information and determine the numberof times the first garbage collection policy has been selected per oneselection of the second garbage collection policy.

At step 1011, the memory controller may determine whether the ratio atwhich the first garbage collection policy has been selected per singleselection of the second garbage collection policy exceeds the secondthreshold value. If the ratio at which the first garbage collectionpolicy has been selected per single selection of the second garbagecollection policy exceeds the second threshold value (“Y” of step 1011),step 1013 may proceed, or if not (“N” at step 1011), step 1021 mayproceed.

At step 1013, the memory controller may increase the first thresholdvalue. For example, the memory controller may increase the firstthreshold value by a set value. Subsequently, step 1001 for a subsequentgarbage collection operation may proceed.

At step 1021, the memory controller may determine whether the ratio atwhich the first garbage collection policy has been selected per singleselection of the second garbage collection policy is less than thesecond threshold value. If the ratio at which the first garbagecollection policy has been selected per single selection of the secondgarbage collection policy is less than the second threshold value (“Y”of step 1021), step 1023 may proceed, or if not (“N” at step 1021), step1001 for a subsequent garbage collection operation may proceed withoutmodifying the first threshold value.

At step 1023, the memory controller may reduce the first thresholdvalue. For example, the memory controller may reduce the first thresholdvalue by a set value. Subsequently, step 1001 for the subsequent garbagecollection operation may proceed.

FIG. 11 is a diagram for describing a memory device 2200 in accordancewith an embodiment of the present disclosure. The memory device 2200shown in FIG. 11 may be applied to the memory system shown in FIGS. 1and 2 .

The memory device 2200 may include a control logic 2210, peripheralcircuits 2220, and a memory cell array 2240. The peripheral circuits2220 may include a voltage generation circuit 2222, a row decoder 2224,an input/output circuit 2226, a column decoder 2228, a page buffer group2232, and a current sensing circuit 2234.

The control logic 2210 may control the peripheral circuits 2220 undercontrol of the memory controller 2100 shown in FIGS. 1 and 2 .

The control logic 2210 may control the peripheral circuits 2220 inresponse to a command CMD and an address ADD which are received from thememory controller 2100 through the input/output circuit 2226. Forexample, the control logic 2210 may output an operating signal OP_CMD, arow address RADD, a column address CADD, page buffer control signalsPBSIGNALS, and an enable bit VRY_BIT<#> in response to the command CMDand the address ADD. The control logic 2210 may determine whether averify operation has passed or failed, in response to a pass signal PASSor a fail signal FAIL received from the current sensing circuit 2234.

The peripheral circuits 2220 may perform a program operation for storingdata in the memory cell array 2240, a read operation for outputting thedata stored in the memory cell array 2240, or an erase operation forerasing the data stored in the memory cell array 2240.

The voltage generation circuit 2222 may generate various operatingvoltages Vop to be used for the program operation, the read operation,or the erase operation in response to an operating signal OP_CMDreceived from the control logic 2210. For example, the voltagegeneration circuit 2222 may transmit a program voltage, a verifyvoltage, a pass voltage, a read voltage, an erase voltage, a turn-onvoltage, etc. to the row decoder 2224.

The row decoder 2224 may transmit, in response to a row address RADDreceived from the control logic 2210, operating voltages Vop to locallines LL coupled to a selected one of the memory blocks included in thememory cell array 2240. The local lines LL may include local word lines,local drain select lines, and local source select lines. In addition,the local lines LL may include various lines such as source linescoupled to the memory blocks.

The input/output circuit 2226 may transmit, to the control logic 2210, acommand CMD and an address ADD received from the memory controllerthrough input/output lines IO, or may exchange data DATA with the columndecoder 2228.

The column decoder 2228 may transmit data between the input/outputcircuit 2226 and the page buffer group 2232 in response to a columnaddress CADD received from the control logic 2210. For example, thecolumn decoder 2228 may exchange data with page buffers PB1 to PBmthrough data lines DL or exchange data with the input/output circuit2226 through column lines CL.

The page buffer group 2232 may be coupled to the bit lines BL1 to BLmcoupled in common to the memory blocks BLK1 to BLKi. The page buffergroup 2232 may include the plurality of page buffers PB1 to PBm coupledto the bit lines BL1 to BLm. For example, a single page buffer may becoupled to each bit line. The page buffers PB1 to PBm may operate inresponse to page buffer control signals PBSIGNALS received from thecontrol logic 2210. For example, during a program operation, the pagebuffers PB1 to PBm may temporarily store program data received from thememory controller, and adjust voltages to be applied to the bit linesBL1 to BLm according to the program data. Furthermore, during a readoperation, the page buffers PB1 to PBm may temporarily store datareceived through the bit lines BL1 to BLm or sense voltages or currentof the bit lines BL1 to BLm.

During a read operation or a verify operation, the current sensingcircuit 2234 may generate a reference current in response to an enablebit VRY_BIT<#> received from the control logic 2210, and may compare asensing voltage VPB received from the page buffer group 2232 with areference voltage generated by the reference current and output a passsignal PASS or a fail signal FAIL.

The memory cell array 2240 may include a plurality of memory blocks BLK1to BLKi configured to store data. User data and various informationneeded for operations of the memory device 2200 may be stored in thememory blocks BLK1 to BLKi. The memory blocks BLK1 to BLKi may beembodied in a two-dimensional structure or a three-dimensionalstructure, and have the same configuration.

FIG. 12 is a diagram illustrating a memory block BLKi in accordance withan embodiment of the present disclosure.

The memory cell array may include a plurality of memory blocks. In FIG.12 , there is illustrated any one memory block BLKi of the plurality ofmemory blocks.

In the memory block BLKi, a plurality of word lines arranged parallel toeach other may be coupled between a first select line and a secondselect line. Here, the first select line may be a source select lineSSL, and the second select line may be a drain select line DSL. In moredetail, the memory block BLKi may include a plurality of strings STcoupled between the bit lines BL1 to BLm and the source line SL. The bitlines BL1 to BLm may be respectively coupled to the strings ST, and thesource lines SL may be coupled in common to the strings ST. The stringsST may have the same configuration; therefore, the string ST that iscoupled to the first bit line BL1 will be described in detail by way ofexample.

The string ST may include a source select transistor SST, a plurality ofmemory cells F1 to F16, and a drain select transistor DST which arecoupled in series to each other between the source line SL and the firstbit line BL1. At least one source select transistor SST and at least onedrain select transistor DST may be included in each string ST, and alarger number of memory cells than the number of memory cells F1 to F16shown in the drawing may be included in each string ST.

A source of the source select transistor SST may be coupled to thesource line SL, and a drain of the drain select transistor DST may becoupled to the first bit line BL1. The memory cells F1 to F16 may becoupled in series between the source select transistor SST and the drainselect transistor DST. Gates of the source select transistors SSTincluded in different strings ST may be coupled to the source selectline SSL, gates of the drain select transistors DST may be coupled tothe drain select line DSL, and gates of the memory cells F1 to F16 maybe coupled to the plurality of word lines WL1 to WL16. Among the memorycells included in different strings ST, a group of memory cells coupledto each word line may be referred to as a physical page PPG. Therefore,the number of physical pages PPG included in the memory block BLKi maycorrespond to the number of word lines WL1 to WL16.

Each memory cell may store 1-bit data. This memory cell is called asingle level cell SLC. In this case, each physical page PPG may storedata of a singe logical page LPG. Data of each logical page LPG mayinclude data bits corresponding to the number of cells included in asingle physical page PPG. For example, in the case where 2 or more bitdata can be stored in each memory cell, each physical page PPG may storedata of two or more logical pages LPG. For instance, in an MLC typememory device, data of two logical pages may be stored in each physicalpage PPG. In a TLC type memory device, data of three logical pages maybe stored in each physical page PPG.

FIG. 13 is a diagram illustrating a memory block having athree-dimensional structure in accordance with an embodiment of thepresent disclosure.

The memory cell array 2240 may include a plurality of memory blocks BLK1to BLKi. The first memory block BLK1 will be described by way ofexample. The first memory block BLK1 may include a plurality of stringsST11 to ST1 m and ST21 to ST2 m. In an embodiment, each of the stringsST11 to ST1 m and ST21 to ST2 m may be formed in a ‘U’ shape. In thefirst memory block BLK1, m strings may be arranged in a row direction(i.e. an X direction). In FIG. 13 , there has been illustrated the casewhere two strings are arranged in a column direction (i.e., a Ydirection), this is only for the sake of explanation. For example, threeor more strings may be arranged in the column direction (the Ydirection).

Each of the strings ST11 to ST1 m and ST21 to ST2 m may include at leastone source select transistor SST, first to n-th memory cells MC1 to MCn,a pipe transistor PT, and at least one drain select transistor DST.

The source select transistor SST, the drain select transistor DST andthe memory cells MC1 to MCn may have structures similar to each other.For example, each of the source select transistor SST, the drain selecttransistor DST and the memory cells MC1 to MCn may include a channellayer, a tunnel insulating layer, a charge trap layer, and a blockinginsulating layer. For example, a pillar for providing the channel layermay be provided in each string. For instance, a pillar for providing atleast one of the channel layer, the tunnel insulating layer, the chargetrap layer, and the blocking insulating layer may be provided in eachstring.

The source select transistor SST of each string may be coupled betweenthe source line SL and the memory cells MC1 to MCp.

In an embodiment, source select transistors of strings arranged in thesame row may be coupled to a source select line extending in the rowdirection. Source select transistors of strings arranged in differentrows may be coupled to different source select lines. In FIG. 13 ,source select transistors of the strings ST11 to ST1 m in a first rowmay be coupled to a first source select line SSL1. Source selecttransistors of the strings ST21 to ST2 m in a second row may be coupledto a second source select line SSL2.

In an embodiment, the source select transistors of the strings ST11 toST1 m and ST21 to ST2 m may be coupled in common to a single sourceselect line.

The first to n-th memory cells MC1 to MCn in each string may be coupledbetween the source select transistor SST and the drain select transistorDST.

The first to n-th memory cells MC1 to MCn may be divided into first top-th memory cells MC1 to MCp and p+1-th to n-th memory cells MCp+1 toMCn. The first to p-th memory cells MC1 to MCp may be successivelyarranged in a vertical direction (i.e., in a Z direction) and coupled inseries to each other between the source select transistor SST and thepipe transistor PT. The p+1-th to n-th memory cells MCp+1 to MCn may besuccessively arranged in the vertical direction (the Z direction) andcoupled in series to each other between the pipe transistor PT and thedrain select transistor DST. The first to p-th memory cells MC1 to MCpand the p+1-th to n-th memory cells MCp+1 to MCn may be coupled to eachother through the pipe transistor PT. Gates of the first to n-th memorycells MC1 to MCn of each string may be respectively coupled to first ton-th word lines WL1 to WLn.

In an embodiment, at least one of the first to n-th memory cells MC1 toMCn may be used as a dummy memory cell. In the case where the dummymemory cell is provided, the voltage or the current of the correspondingstring may be stably controlled. A gate of the pipe transistor PT ofeach string may be coupled to a pipeline PL.

The drain select transistor DST of each string may be coupled betweenthe corresponding bit line and the memory cells MCp+1 to MCn. Stringsarranged in the row direction may be coupled to corresponding drainselect lines extending in the row direction. The drain selecttransistors of the strings ST11 to ST1 m in the first row may be coupledto a first drain select line DSL1. The drain select transistors of thestrings ST21 to ST2 m in the second row may be coupled to a second drainselect line DSL2.

Strings arranged in the column direction may be coupled to correspondingbit lines extending in the column direction. In FIG. 13 , the stringsST11 and ST21 in a first column may be coupled to a first bit line BL1.The strings ST1 m and ST2 m in an m-th column may be coupled to an m-thbit line BLm.

Among the strings arranged in the row direction, memory cells coupled tothe same word line may form one page. For example, memory cells coupledto the first word line WL1 in the strings ST11 to ST1 m of the first rowmay form a single page. Memory cells coupled to the first word line WL1in the strings ST21 to ST2 m of the second row may form another singlepage. When any one of the drain select lines DSL1 and DSL2 is selected,strings arranged in the corresponding row may be selected. When any oneof the word lines WL1 to WLn is selected, a corresponding single pagemay be selected from the selected strings.

FIG. 14 is a diagram illustrating a memory block having athree-dimensional structure in accordance with an embodiment of thepresent disclosure.

The memory cell array 2240 may include a plurality of memory blocks BLK1to BLKi. The first memory block BLK1 will be described by way ofexample. The first memory block BLK1 may include a plurality of stringsST11′ to ST1 m′ and ST21′ to ST2 m′. Each of the strings ST11′ to ST1 m′and ST21′ to ST2 m′ may extend in a vertical direction (i.e., in a Zdirection). In each memory block BLKi, m′ strings may be arranged in arow direction (i.e., in an X direction). In FIG. 14 , there has beenillustrated the case where two strings are arranged in a columndirection (i.e., in a Y direction), this is only for the sake ofexplanation. For example, three or more strings may be arranged in thecolumn direction (the Y direction).

Each of the strings ST11′ to ST1 m′ and ST21′ to ST2 m′ may include atleast one source select transistor SST, first to n-th memory cells MC1to MCn, and at least one drain select transistor DST.

The source select transistor SST of each string may be coupled betweenthe source line SL and the memory cells MC1 to MCn. Source selecttransistors of strings arranged in the same row may be coupled to thesame source select line. The source select transistors of the stringsST11′ to ST1 m′ arranged in a first row may be coupled to a first sourceselect line SSL1. The source select transistors of the strings ST21′ toST2 m′ arranged in a second row may be coupled to a second source selectline SSL2. In an embodiment, the source select transistors of thestrings ST11′ to ST1 m′ and ST21′ to ST2 m′ may be coupled in common toa single source select line.

The first to n-th memory cells MC1 to MCn in each string may be coupledin series between the source select transistor SST and the drain selecttransistor DST. Gates of the first to n-th memory cells MC1 to MCn maybe respectively coupled to first to n-th word lines WL1 to WLn.

In an embodiment, at least one of the first to n-th memory cells MC1 toMCn may be used as a dummy memory cell. In the case where the dummymemory cell is provided, the voltage or the current of the correspondingstring may be stably controlled. Thereby, the reliability of data storedin the first memory block BLK1 may be improved.

The drain select transistor DST of each string may be coupled betweenthe corresponding bit line and the memory cells MC1 to MCn. Drain selecttransistors DST of strings arranged in the row direction may be coupledto corresponding drain select lines extending in the row direction. Thedrain select transistors DST of the strings ST11′ to ST1 m′ in the firstrow may be coupled to a first drain select line DSL1. The drain selecttransistors DST of the strings ST21′ to ST2 m′ in the second row may becoupled to a second drain select line DSL2.

In other words, the first memory block BLK1 of FIG. 14 may have anequivalent circuit similar to that of the first memory block BLK1 ofFIG. 13 except that a pipe transistor PT is excluded from each cellstring.

FIG. 15 is a diagram illustrating an example of a memory system 30000including the memory controller shown in FIGS. 1 and 2 .

Referring to FIG. 15 , the memory system 30000 may be embodied in acellular phone, a smartphone, a tablet personal computer (PC), apersonal digital assistant (PDA) or a wireless communication device. Thememory system 30000 may include a memory device 2200 and a memorycontroller 2100 configured to control the operation of the memory device2200.

The memory controller 2100 may control a data access operation, e.g., aprogram operation, an erase operation, or a read operation, of thememory device 2200 under control of a processor 3100.

Data programmed in the memory device 2200 may be outputted through adisplay 3200 under control of the memory controller 2100.

A radio transceiver 3300 may send and receive radio signals through anantenna ANT. For example, the radio transceiver 3300 may change a radiosignal received through the antenna ANT into a signal capable of beingprocessed in the processor 3100. Therefore, the processor 3100 mayprocess a signal outputted from the radio transceiver 3300 and transmitthe processed signal to the memory controller 2100 or the display 3200.The memory controller 2100 may transmit a signal processed by theprocessor 3100 to the memory device 2200. Furthermore, the radiotransceiver 3300 may change a signal outputted from the processor 3100into a radio signal, and output the changed radio signal to an externaldevice through the antenna ANT. An input device 3400 may be used toinput a control signal for controlling the operation of the processor3100 or data to be processed by the processor 3100. The input device3400 may be embodied in a pointing device such as a touch pad and acomputer mouse, a keypad or a keyboard. The processor 3100 may controlthe operation of the display 3200 such that data outputted from thememory controller 2100, data outputted from the radio transceiver 3300,or data outputted form the input device 3400 is outputted through thedisplay 3200.

In an embodiment, the memory controller 2100 capable of controlling theoperation of the memory device 2200 may be embodied as a part of theprocessor 3100 or a chip provided separately from the processor 3100.

FIG. 16 is a diagram illustrating an example of a memory system 40000including the memory controller shown in FIGS. 1 and 2 .

Referring to FIG. 16 , the memory system 40000 may be embodied in apersonal computer (PC), a tablet PC, a net-book, an e-reader, a personaldigital assistant (PDA), a portable multimedia player (PMP), an MP3player, or an MP4 player.

The memory system 40000 may include a memory device 2200, and a memorycontroller 2100 configured to control a data processing operation of thememory device 2200.

A processor 4100 may output data stored in the memory device 2200through a display 4300, according to data input from an input device4200. For example, the input device 4200 may be embodied in a pointingdevice such as a touch pad or a computer mouse, a keypad, or a keyboard.

The processor 4100 may control the overall operation of the memorysystem 40000 and control the operation of the memory controller 2100. Inan embodiment, the memory controller 2100 capable of controlling theoperation of the memory device 2200 may be embodied as a part of theprocessor 4100 or a chip provided separately from the processor 4100.

FIG. 17 is a diagram illustrating an example of a memory system 50000including the memory controller shown in FIGS. 1 and 2 .

Referring to FIG. 17 , the memory system 50000 may be embodied in animage processing device, e.g., a digital camera, a portable phoneprovided with a digital camera, a smartphone provided with a digitalcamera, or a tablet PC provided with a digital camera.

The memory system 50000 may include a memory device 2200, and a memorycontroller 2100 configured to control a data processing operation, e.g.,a program operation, an erase operation, or a read operation, of thememory device 2200.

An image sensor 5200 of the memory system 50000 may convert an opticalimage into digital signals. The converted digital signals may betransmitted to a processor 5100 or the memory controller 2100. Undercontrol of the processor 5100, the converted digital signals may beoutputted through a display 5300 or stored in the memory device 2200through the memory controller 2100. Data stored in the memory device2200 may be outputted through the display 5300 under control of theprocessor 5100 or the memory controller 2100.

In an embodiment, the memory controller 2100 capable of controlling theoperation of the memory device 2200 may be embodied as a part of theprocessor 5100 or a chip provided separately from the processor 5100.

FIG. 18 is a diagram illustrating an example of a memory system 70000including the memory controller shown in FIGS. 1 and 2 .

Referring to FIG. 18 , the memory system 70000 may be embodied in amemory card or a smart card. The memory system 70000 may include amemory device 2200, a memory controller 2100, and a card interface 7100.

The controller 2100 may control data exchange between the memory device2200 and the card interface 7100. In an embodiment, the card interface7100 may be a secure digital (SD) card interface or a multi-media card(MMC) interface, but it is not limited thereto.

The card interface 7100 may interface data exchange between a host 60000and the memory controller 2100 according to a protocol of the host60000. In an embodiment, the card interface 7100 may support a universalserial bus (USB) protocol, and an interchip (IC)-USB protocol. Here, thecard interface 7100 may refer to hardware capable of supporting aprotocol which is used by the host 60000, software installed in thehardware, or a signal transmission method.

When the memory system 70000 is connected to a host interface 6200 ofthe host 60000 such as a PC, a tablet PC, a digital camera, a digitalaudio player, a cellular phone, console video game hardware or a digitalset-top box, the host interface 6200 may perform data communication withthe memory device 2200 through the card interface 7100 and the memorycontroller 2100 under control of a microprocessor (μP) 6100.

In accordance with the present disclosure, an efficient garbagecollection operation corresponding to data attributes may be performed.

Examples of embodiments have been disclosed herein, and althoughspecific terms are employed, they are used and are to be interpreted ina generic and descriptive sense only and not for purpose of limitation.In some instances, as would be apparent to one of ordinary skill in theart as of the filing of the present application, features,characteristics, and/or elements described in connection with aparticular embodiment may be used singly or in combination withfeatures, characteristics, and/or elements described in connection withother embodiments unless otherwise specifically indicated. Accordingly,it will be understood by those of skill in the art that various changesin form and details may be made without departing from the spirit andscope of the present disclosure as set forth in the following claims.

What is claimed is:
 1. An operating method of a memory device, theoperating method comprising: selecting a victim block, wherein, when anumber of free blocks is equal to or greater than a first threshold, atleast one first memory block, in which a number of pages storing colddata is greater than a first threshold number, is selected as the victimblock, and when the number of free blocks is less than the firstthreshold, at least one second memory block, in which a number of validpages is less than a second threshold number, is selected as the victimblock; performing a garbage collection operation on the selected victimblock; and adjusting the first threshold based on a selection number oftimes between the selected first memory blocks and the selected secondmemory blocks, wherein the first threshold is increased when theselection number is greater than a second threshold and decreased whenthe selection number is less than the second threshold, whereinattributes of data indicating whether the data is hot data or cold dataare determined by a host.
 2. The operating method of claim 1, furthercomprising: extracting, for the attributes of the data, attributeinformation included in a program request received from the host.
 3. Theoperating method of claim 2, further comprising storing the hot data andthe cold data along with the attributes in one memory block, wherein theattributes comprise a hot data attribute and a cold data attribute. 4.The operating method of claim 3, further comprising, within the selectedvictim block, preferentially performing garbage collection on the colddata having the cold data attribute.
 5. The operating method of claim 4,wherein the preferentially performing of the garbage collectioncomprises transferring the cold data with the cold data attribute fromthe victim block and storing the cold data and the cold data attributein a target block.
 6. The operating method of claim 1, furthercomprising determining victim data in the victim block for garbagecollection based on a cold data attribute included in a program requestreceived from the host.
 7. The operating method of claim 1, wherein theperforming of the garbage collection operation comprises utilizing agarbage collection policy in which a priority of the cold data is higherthan a priority of the hot data.
 8. The operating method of claim 1,wherein the performing of the garbage collection operation comprisesutilizing a garbage collection policy in which a memory block having asmaller number of valid pages has a higher priority for being selectedas the victim block.
 9. The operating method of claim 1, wherein theperforming of the garbage collection operation comprises utilizing agarbage collection policy in which a memory block having a greaternumber of pages storing the cold data has a higher priority for beingselected as the victim block.